Category Archives: LNHS

LNHS Virtual Talk – ‘When Will It Flower? Plants and Climate Change’, by Alastair Fitter

Dear Readers, every gardener or natural history enthusiast that I bump into has something to say about the way that plants are changing their habits. So often, though, the information is anecdotal, because we don’t tend to actually record things when they happen. So, it was wonderful to attend this talk by Alastair Fitter, son of Richard Fitter, who wrote the first book about London’s wildlife in the New Naturalist series back in the 1940s and who was, among many other things, president of the London Natural History Society. From 1954 to 2000, Richard Fitter recorded the first flowering dates of various wildflowers growing in his garden and this produced a data set that turned into the first major study of the impact of climate change on the flora of the UK. That document was published in 2002, a collaboration between Richard and Alastair Fitter, when Fitter Senior was nearly 90 years old. The Fitters were interviewed on Radio Four’s Today programme, and when Richard was asked why he’d done all that recording, he replied that as a boy he’d been told that it was always good to write things down. As Alastair Fitter remarked, thank goodness he did!

Another very useful resource is the Woodland Trust’s ‘Nature’s Calendar’, which recorded ‘First Flowering Days’ for a selection of different plants between 2001 and 2016.

What is very clear is that plants are coming into flower earlier, and that this process has speeded up over the past 25 years. From the Woodland Trust data, we see that:

Hazel (Corylus avellana) produced its catkins 31 days earlier in 2016 compared to 2000.

Hazel (Corylus avellana) (Photo One)

Lesser celandine (Ficaria verna) has advanced its flowering date by 27 days between 2001 – 2016, but Richard Fitter recorded the flowering had already come forward by 20 days between 1954 and 2000, making a total advance of an astonishing 47 days between 1954 and 2016.

Photo Two by By Michal Osmenda from Brussels, Belgium -, CC BY-SA 2.0,

Lesser celandine (Ficaria verna) (Photo Two)

English bluebells have advanced their flowering date by three weeks since 2001.

Photo Three by MichaelMaggs, CC BY-SA 3.0 <>, via Wikimedia Commons

English bluebell (Hyacinthiodes non-scripta) (Photo Three)

From Fitter’s data, if you took all the different species in the sample, there had been a general movement towards earlier flowering of about 6 days by 2000, but this hid some major movements by individual plants. For example, white deadnettle (Lamium album) flowered 55 days earlier in the 1990s than it had in the 1950s (and indeed now flowers all year round).

Photo One by Rosser1954, CC BY-SA 4.0 <>, via Wikimedia Commons

White deadnettle (Photo Four)

There are some very strange anomalies, however: our old friend Buddleia flowered a whole 36 days later in the 1990s compared to the 1950s, and it’s still unclear why. All theories duly considered!

Photo Five by Agnieszka Kwiecień, Nova, CC BY-SA 4.0 <>, via Wikimedia Commons

Butterfly Bush (Buddleia davidii) (Photo Five)

And while we’re on the subject of garden plants, Fitter describes how Fred Last studied his garden and recorded first flowering dates from 1978 to 2007. Mahonia advanced its flowering time during this period by an extraordinary 3 months (which now makes it one of the handiest garden plants for early bumblebees).

Photo Six by Photo by David J. Stang, CC BY-SA 4.0 <>, via Wikimedia Commons

Mahonia japonica (Photo Six)

More recent data comparisons by Alastair Fitter show that over 50% of plants are coming into flower by the end of April, an advance of about 5 weeks. But the question is, why?

Fitter explained that flowering times are determined by a number of factors. Firstly, there’s the question of when the flower buds form. For spring bulbs, next year’s flowers are formed during the previous summer, but the actual flowering time is determined by the temperature in the spring.  Fitter used the example of the Tulip Society shows to illustrate this. The date of the Wakefield and North of England Tulip Society’s annual show is determined by when the ‘English florist tulips’ are thought to be coming into their best. The Society was founded in 1836, and Fitter showed a lovely slide, where the date of the show has been coming forward on a smooth curve that exactly matches the average mean temperature in March: for every degree increase, the show comes forward by three days. The show is now commonly held in the second week of May, compared with the very end of May in the mid 1800s.

Photo Seven from

Tulips at the 181st Wakefield and North of England Tulip Society Show (Photo Seven)

Another factor that determines flowering time is day-length, with some plants coming into flower as the days lengthen, and others as the days get shorter. Fitter points out that for the majority of plants, we simply don’t know how day-length affects them but for a few, such as red campion (which responds to lengthening days) and hops (which react to shortening days) we can see a correlation.

Temperature is, however, critical. Fitter showed how the flowering time of Coltsfoot was dependent on the mean temperature in February but, more generally, an increase in temperature of 1 degree in the four months before flowering could advance the flowering date by about three days. However, a warm summer and autumn could act to delay flowering by about the same amount. Go figure!  I wondered if a warm summer and autumn might mean lower rainfall, which could delay bud formation. What is clear is that a lot more research is needed, and there is still a lot that we don’t know. The pattern is clear, however: most plants are flowering earlier, and flowering patterns are becoming a lot less predictable.

Photo Eight by Andreas Trepte, CC BY-SA 2.5 <>, via Wikimedia Commons

Coltsfoot (Tussilago farfara) (Photo Eight)

Fitter’s final point was, do these earlier flowering times matter? And of course, there are a number of problems not just with earlier flowering, but also with the increased unpredictability of flowering times. Some pollinators, for example, will take advantage of earlier flowering, but where there is a very specific relationship, such as that which occurs with orchids, the plant may come into flower but the pollinator will not yet have emerged. Sometimes, as in the case of the orange-tip butterfly, the insect is responding to earlier flowering times of cuckooflower, so that its caterpillars, which feed on the seedpods of the plant, are still ‘in sync’.

Photo Nine by Jessica Towne, CC0, via Wikimedia Commons

Female orange-tip butterfly (Anthocharis cardamines) (Photo Nine)

However, something that had never occurred to me was that, as flowering times change, some plants will be more or less likely to hybridise because their flowering times will move further apart, or begin to overlap. Sweet violets (Viola odorata) will be less likely to crossbreed with hairy violets (Viola hirsuta) because their flowering times are now 15 days further apart. Red campion (Silene dioica) and white campion (Silene latifolia) are, however, coming closer together, and so hybridisation is more likely. As Fitter points out, hybridisation is a major driver of evolutionary change, and so some groups may become less able to adapt over time as their flowering times grow further apart.

Photo Ten by The original uploader was Sannse at English Wikipedia., CC BY-SA 3.0 <>, via Wikimedia Commons

Hybrid Campion ( red campion (Silene dioica) and white campion (Silene latifolia) (Photo Ten)

And so, Fitter ended by saying that earlier flowering times are a clear harbinger of climate change, and an indicator that things were changing rapidly in the natural world. We owe a debt of gratitude to Richard Fitter for ‘writing things down’, and it seems to me that this illustrates yet again the importance of citizen science, of recording these extraordinary times that we live in. And Fitter finished as he’d started, with a quote from Shakespeare, in which Titania blames Oberon for the strange changes in the climate. I think we need to look a little closer to home.

‘And thorough this distemperature we see
The seasons alter: hoary-headed frosts
Far in the fresh lap of the crimson rose,
And on old Hiems’ thin and icy crown
An odorous chaplet of sweet summer buds
Is, as in mockery, set: the spring, the summer,
The childing autumn, angry winter, change
Their wonted liveries, and the mazed world,
By their increase, now knows not which is which.’

I cannot recommend this talk highly enough, and you can watch the whole thing here.

Photo Credits

Photo One by Agnes Monkelbaan, CC BY-SA 4.0 <>, via Wikimedia Commons

Photo Two by By Michal Osmenda from Brussels, Belgium –, CC BY-SA 2.0,

Photo Three by MichaelMaggs, CC BY-SA 3.0 <>, via Wikimedia Commons

Photo Four by Rosser1954, CC BY-SA 4.0 <>, via Wikimedia Commons

Photo Five by Agnieszka Kwiecień, Nova, CC BY-SA 4.0 <>, via Wikimedia Commons

Photo Six by Photo by David J. Stang, CC BY-SA 4.0 <>, via Wikimedia Commons

Photo Seven from

Photo Eight by Andreas Trepte, CC BY-SA 2.5 <>, via Wikimedia Commons

Photo Nine by Jessica Towne, CC0, via Wikimedia Commons

Photo Ten by The original uploader was Sannse at English Wikipedia., CC BY-SA 3.0 <>, via Wikimedia Commons

LNHS Talks – ‘Bats in Churches’ by Claire Boothby

Dear Readers, when I hear the phrase ‘Human/Wildlife Conflict’ I think of villagers fighting off elephants who are raiding their crops in Sri Lanka, or oil plantation workers chasing orang utans with machetes. But there are plenty of occasions in the UK when our hard-pressed wild creatures come into rather more contact with humans than is good for either party. I do love a talk that makes me think about something that I’d never considered before, and so it was with this one. Claire Boothby, who works for the organisation ‘Bats in Churches’ has the remit of trying to mitigate the problems that occur when bats roost in churches, and she had some very interesting things to say on the issue.

Bats have always used churches as roosts – they seem to prefer older churches with wooden roofs. One conservationist suggested that those timber beams reminded the bats of ancient woodland, which is where they would probably roost preferentially if there was enough of the habitat left. If the church is surrounded by a nice big churchyard with lots of flying insects, so much the better. In the summer, the female bats like the warmer part of the church as it’s ideal as a maternity roost. In the winter, they may favour places like crypts and undercrofts as hibernation sites.

Many churches have voids in the roof with direct access to the outside world, and in these cases the parishioners might not even know that there is a bat roost. The trouble comes if the bats have access to the interior of the church. My heart is obviously with the bats, but Boothby showed how the droppings from the bats can damage brass memorial plaques, marble tombs and stained glass windows. Many of the volunteers who clean churches are elderly, and the church can lose significant income from weddings and events if the building is soiled. One church in the study closed because of the damage from a substantial bat roost.

What to do? The bats are protected (thank goodness) but the buildings are part of our heritage, and are often also the centre of a small community. Fortunately, Bats in Churches works with all the parties involved. Funded by the National Lotteries Fund, it brings together the Bat Conservation Trust, the Church of England, Historic England and the Church Conservation Trust, and it works very closely with the parishioners and clergy at the church.

It’s easy to demonise those in the churches who are complaining about the bats, but in the video interviews with them, they were all quietly apologetic about even mentioning the problems that they were experiencing. They wanted to conserve the bats, but they were also worried about the churches, one of which was an extremely rare brick-built Tudor church. They were also worried about the cleaning burden that fell on a group of volunteers who might scrub for hours only to find that, when they returned a few days later, things were just as bad.

Photo One by By John Winfield, CC BY-SA 2.0,

St Nicholas, Chignal Smeally (Photo One)

So, what to do? In churches where the bat population wasn’t causing too many problems, such as Holy Trinity Tattershall, the bats were turned into a feature, with a bat information board inside the church, bat walks outside it, bat teeshirts and a ‘Tatty Bat’ mascot that people could buy.

Photo Two from

‘Tatty Bat’ merchandise from Holy Trinity, Tattershall (Photo Two)

In churches where the problem was worse, however, there were capital works on the building. Bat surveyors would get an idea of the size of the roost, the species involved and their entrance and exit points. They would be watched to see how they were behaving, and then a plan was drawn up that would minimise the damage in the church without affecting the bats. In some cases, this could involve something as simple as a screen so that when the bats left the roost they were funnelled towards the outside exit, rather than flying around in the church first. In another, a bat box with heraldic symbols on it was created so that the bats had a perfect roost with the same entrance as previously. In the most expensive example, St Lawrence Radstone church had so many bats, and so many droppings, that the church had actually been closed. Part of the church had a twelfth century ceiling, but the bats were in the much later Victorian part of the roof. A plan was drawn up to create a false ceiling in the Victorian bit, so that the bats still had a void to fly around in, but could enter and exit from their original points. This was so successful that the church was able to reopen in 2020, without any damage to the bats. You can watch a video about the project here.

Photo Three by By Ben Nicholson, CC BY-SA 2.0,

St. Lawrence Church, Radstone (Photo Three)

All of the projects mentioned are subject to monitoring for at least three years, and hopefully longer, to ensure that the bat populations haven’t been harmed by the changes. I must say that I was impressed by the imagination and dedication shown by all parties, who clearly wanted to achieve a solution.

Bats in Churches would really like some help surveying churches: you don’t need to be a qualified bat surveyor, and it sounds like an interesting and worthwhile project. They are trying to survey a sample of 1000 churches (they ground to a halt during the pandemic along with everybody else) and, excitingly, you get the loan of a bat detector and are taught how to submit bat droppings for DNA testing. Who could resist? If you think you fancy it, all the details are on the Bats in Churches website here.

Claire Boothby was a very engaging speaker who is clearly passionate about finding solutions to the tricky problems of bats, people and medieval buildings. It was a real pleasure to watch her talk, and if you’d like to do the same, you can find it here. These LNHS talks have been so fascinating and varied that I hope they continue even after the pandemic – it’s clear that they can reach and educate a much wider audience than their London evening in-person events did. Fingers crossed that we can soon have both!

Photo Credits

Photo One By John Winfield, CC BY-SA 2.0,

Photo Two from

Photo Three By Ben Nicholson, CC BY-SA 2.0,

LNHS Talks – Urban Foxes by Professor Dawn Scott

Dear Readers, as you will know I am a great fan of our urban foxes, and so I was looking forward to this talk very much. Prof. Scott did one of the earliest and most extensive studies of urban foxes in Bristol, and much of what she found has greatly informed our understanding of these animals.

Prof. Scott is very interested in how animals adapt to urban landscapes, and why some do better than others. She describes cities as ‘landscapes of fear and opportunity’. The opportunities include that cities are warmer, there are less predators, more food (especially as people deliberately feed year-round), lots of niches for refuge, and consistent water supplies. There is, however, less natural food, more competition, a higher risk of disease as territories tend to be smaller, danger from the roads, from some pets, and also, of course, a high risk of conflict with people. The animals that tend to do best are enterprising generalists – this includes foxes, but also badgers (who are increasingly being seen in the suburbs) and hedgehogs (who are now commoner in urban areas than in many places in the countryside).

Prof. Scott described how adaptation to city life for an animal usually includes an increased density of animals (as there are more food resources), higher aggression (because of competition for those resources) and much less fear of humans – this is known as ‘synurbanisation’. She considers that the extraordinary ability of the fox to navigate the 3-dimensional structures of the city to be one of its key skills in making the city its home – she tells of finding foxes living on roofs and in trees. Anyone who has seen a fox effortlessly bound over a six-foot fence will be nodding their heads in agreement.

Prof. Scott believes that an understanding of the fox would help to offset some of the hostility that people feel towards the animal. Socially, foxes tend to live in groups of 3 or 4 – typically a small ‘family’. However, foxes forage for food on their own once they’re into adolescence. They communicate mainly by smell, which explains the piles of poo and that heavy ‘foxy’ smell that they produce – it’s thought that the scent messages might include sex, breeding status and even dominance. As anyone who has been woken up in the night also knows, foxes communicate by sound too – there are over 28 different calls, including the screaming of vixens, the barking of dog foxes and the various bouts of yipping that can enliven many an early morning. However, the screaming is only likely to be heard in December – February, when the vixens are in heat and, apart from a lot of chaos when the cubs leave the den in May, foxes are generally fairly quiet for the rest of the year. Females will have a natal den where the cubs are born (frequently under a garden shed it seems), but they will move the cubs if disturbed, and adult foxes will have several rest sites in their territory where they hide during the day. They are largely, but not exclusively, nocturnal, as the foxes who turn up in my garden will attest.

Only one in five foxes will live to be two years old, with roads claiming the majority of victims. In captivity, foxes can live ten to fourteen years on average.

On the vexed question of whether we were becoming ‘overrun’ with urban foxes, Prof. Scott looked back through the records, and had done several scientific studies of her own. Her view was that urban foxes had certainly spread – in the 1980’s, 91% of cities had no urban foxes, but now most of them did, with the foxes spreading north and west. Her study in Bristol showed that there were approximately 36 foxes per square kilometre. However, in 2010 a devastating outbreak of mange killed 95% of the foxes in the city.

Prof. Scott showed several photos of foxes, some with mange, some who were simply shedding their winter coats. One way of telling is obviously bare, sore flesh, but a real giveaway seems to be if the tails are looking scratty – this is a clear sign of mange. Healthier foxes seem to be able to just shrug it off, but for foxes already weakened by bad nutrition it can be a death sentence. Furthermore, there’s no easy solution: the jury is out on the homeopathic solution that can be given without harm (and possibly without any positive effects either) but the normal veterinary treatment can only be given under controlled circumstances. Furthermore, Prof. Scott found that foxes who were taken into sanctuaries for treatment and then released back into their old territories nearly always found that a new fox had taken over their old home, and the original incumbents were usually driven out, with all the concomitant dangers of being run over as they searched for a new territory. Prof. Scott’s opinion was that, hard as it seems, mange is something that limits the numbers of foxes in an area when they get too high – it thrives in conditions where there are lots of foxes in close proximity. A more ‘usual’ population of foxes seems to be about 12 foxes per square kilometre, something seen in more recent studies in Bristol (post mange) and London.

High concentrations of foxes are often supported by feeding. In a recent study, Prof. Scott found that 36% of the people in her study fed foxes, mostly either by hand or at the back door. One fox in the study spent his whole time waiting outside the house where he was fed at 8 p.m. and then moving to house number two where he was fed at 10 p.m. There are issues around what was fed (foxes definitely like jam sandwiches but are unlikely to make them for themselves), and the danger of allowing foxes to associate people with food. Some of the more lurid headlines seem to feature foxes who feel perfectly comfortable going into people’s houses and making themselves at home, often biting people when cornered. Prof. Scott’s advice is to feed little, feed something appropriate (like dog food) and not to feed too close to the house, and certainly never by hand.

And finally, one of the questions that Prof. Scott is frequently asked is ‘do foxes kill cats?’ Well, we’ll never know for sure that there isn’t a rogue fox out there with a taste for felines, but judging by the trail camera evidence, a solitary cat can see off two foxes who attempt to snaffle her tea. Apparently in all the filmed incidents, the cat beat up the fox. Badgers trump foxes and cats, however, although there was no evidence that badgers actually hurt cats. One film clip showed a hedgehog feeding, at which point a fox picked it up and deposited it elsewhere before coming back to eat the food. It’s easy to see that that’s a situation that could lead to the fox predating the hedgehog.

So, this was a very interesting talk, with a lot of thought given to how people and foxes can live together more harmoniously. Prof. Scott thinks that understanding the fox is key, and I agree – as with everything, knowing the reason for something (such as night time screaming or piles of poo) can make it a lot more bearable. I for one love to see the touch of wildness that the fox brings, and am happy to put up with a little inconvenience for the pleasure of their company.

You can watch the whole of the talk here. Highly recommended.

A young vixen in St Pancras and Islington cemetery. My favourite British wild mammal.



LNHS Talks – Breeding Birds of Hampstead Heath by Jeff Waage

Dear Readers, the London Natural History talk this week was of particular interest to me. When we had a bird survey done in 2019, Coldfall Wood was found to be particularly rich in breeding birds for an urban woodland, but the increased footfall during lockdown, coupled with the threats to the environment itself, have made me worry about the additional pressure that is being put on the animals and plants that live there.

Jeff Waage was part of a team that undertook a survey of Hampstead Heath last year. Part of the reason was to determine which birds were displaying breeding activity, and where: disturbance from walkers and dogs is widespread even if there isn’t a pandemic, and there has been an increased demand for Forest Schools, ‘Forest Bathing’ and professional dogwalking. In the past year the Heath has had an estimated 50 million visitors, which is pretty much equivalent to most of the population of the country popping in. But data can help, and so Waage and his team walked transects of between 1 and 3 kilometres through the Heath on at least six occasions, looking for breeding behaviour.

Photo One by Dudley Miles, CC BY-SA 3.0 <>, via Wikimedia Commons

Kenwood, Hampstead Heath (Photo One)

Breeding behaviour was defined as territorial singing, birds carrying nesting material or food or fecal sacs, birds actually sitting on a nest, territorial disputes or sightings of fledglings. In my experience birds are very good at hiding nests, but you can fairly easily spot them ‘eating for two’ (or a dozen in the case of blue tits).

At the end of the survey, there had been 2169 sightings of 41 species of bird. Compared with the 26 species seen in Coldfall Wood this probably sounds pretty good, but the Heath has a much wider range of habitats. However, it’s clear that the Heath’s biodiversity has been under stress for some time: in 1992, a survey revealed 71 species. Many of those lost have been ground nesting birds, who are always the first victims of too much footfall and too many dogs, but even birds such as the mistle thrush and the common whitethroat appeared to be in decline.

Photo Two  By Andreas Trepte - Own work, CC BY-SA 2.5,

Common Whitethroat (Curruca communis) (Photo Two)

Waage estimated that 40% of the Heath’s bird species were red or amber listed: he explained that this designation was arrived at by looking at both the vulnerability of the species (i.e. was it nesting in an area of high disturbance) combined with its ‘patchiness’ (i.e. were there just a few isolated populations within the Heath). For example, the whitethroats nested in scrubby areas where there was a lot of picnicking and dog walking, and there appeared to be only one pair of sparrowhawks.

Photo Three By Meneer Zjeroen -, CC BY 2.0,

Female sparrowhawk (Accipiter nisus) (Photo Three)

The approach to maintaining and increasing the bird biodiversity of the Heath was multi-pronged.

Firstly, there was a need to identify areas of the Heath where there would be the least impact on breeding birds for commercial activities such as the forest schools, and this was possible following the survey.

Secondly, where birds were vulnerable there was to be a bid to raise public awareness, through new signage and articles in local newspapers.

A third area was to improve and even create habitat, such as reed beds for reed buntings.

Finally, resources such as food and nest boxes could be made available.

There was also a need to investigate what was happening on the fringes of the Heath – there were surprisingly few nesting finches, for example, and the group felt that this was probably because the finches were nesting in local parks and gardens instead, where there was a higher availability of food.

And lastly, and probably most importantly, the Heath needs continued monitoring to see what’s happening with the bird populations. Data can be our most powerful tool in gaining an understanding of what’s happening in an area, and over time. It will be interesting to see what future surveys reveal.

I’ve always been very happy to just enjoy nature, and to be thrilled at the arrival of a new bird or the sight of an unexpected insect. I’m still thrilled, but it seems to me that collecting data is a way of putting meat onto the bones of the anecdotal picture that you build up over the years. Citizen science is becoming increasingly popular, and I hope that, just as the Big Garden Birdwatch has become a major way of recording trends in garden birds, so other surveys will build up a picture of what’s going on with other plants and animals. In fact, there’s an online conference on this very subject being run by the Field Studies Council in May, with the added bonus that it’s concentrating on urban wildlife recording. I’ll be there, and will report back, but for £5 it seems like a bargain for anyone interested in getting involved with recording. With habitat destruction and climate change in full swing there has never been a better time to take notice of what’s going on around us.

Photo Credits

Photo One by Dudley Miles, CC BY-SA 3.0 <>, via Wikimedia Commons

Photo Two By Andreas Trepte – Own work, CC BY-SA 2.5,

Photo Three By Meneer Zjeroen –, CC BY 2.0,

London Natural History Society Talks – ‘Bird Flight and Cooperative Dynamics’ by Steve Portugal

Dear Readers, can I start by saying that this was a fascinating and well-presented talk, with lots of fascinating videos and graphics, and if you have an hour to spare I would hot-foot it over to the LNHS Youtube channel to watch the whole thing. Steve Portugal is such a clear and entertaining speaker that it’s best to get this info direct, but here is my synopsis.

The talk is really about why birds gather in groups, how they behave when they do, and what advantages they gain from their behaviour. There are two main ways of ‘flocking’, and these are dictated largely by size. A bird that is smaller than a black-headed gull is likely to form a ‘cluster’ – we see this in pigeons and starlings and all those other little  birds. Any bird larger than this is likely to fly in a V-formation, so that includes cranes, geese, pelicans, flamingoes and, as we’ll see, ibises.

To start with, Portugal looked at birds that fly in a V-formation. Partly this might be because large birds are much less manoeuvrable – a crane has the same turning circle as a jumbo jet, apparently. Other reasons might be:

  • the dilution effect – if lots of birds fly together, an individual is less likely to be predated  (this applies to cluster flocks too)
  • Navigation – older, more experienced birds fly at the front to teach the younger birds behind the route.
  • Vision – it’s easier to see the lead bird if you fly in a V formation
  • Energetic – birds are able to save energy by flying in this way.

It’s this last point that Portugal is most interested in. When a plane or a bird flies, it pushes the air in front of it out of the way. At the wing-tip something called a wing-tip vortex is created, and this provides an updraft, which makes staying in the air easier. However, most of the air gets pushed down and creates a downdraft, which will push anything following down. It’s this effect that dictates the gap between planes when taking off at an airport, and its the wingtip vortex effect that is thought to be one of the reasons why birds fly in a V formation.

Lest you think that this is all about birds, Portugal explained that aircraft manufacturers are desperate to copy this effect, to save fuel. He showed a short film made by an airline in which a plane takes off from Melbourne and is joined by others from other Australian airports to fly across the Pacific. When the planes join, they get into a V formation, and fly together until they make landfall above the US, at which point the planes peel off to go to their different destinations. However, another film showed a group of small planes trying to do just this, and getting into all kinds of trouble – planes have to get so close together to find the updraft from the wingtip that they risk stalling or tumbling over. It’s thought that only a computer will be able to calculate the manoeuvres required with enough accuracy to avoid disaster.

Photo One By Myself (Adrian Pingstone). - My own photo, taken with a Nikon D5300 DSLR and Nikon 18-200 mm lens, Public Domain,

The Red Arrows display team in a V Formation. Not as easy as it looks! (Photo One)

However, back to the birds. Portugal’s subject study was made possible by the advent of biologgers that are small and light enough to attach to a bird, and also by a study into the Waldrapp Ibis (also known as the Northern Bald Ibis). Historically they were present all through Mediterranean Europe, Northern Africa and the Middle East but, after the recent extinction of the Syrian population, the only wild birds left are in Morocco. This population doesn’t migrate, but it was hoped that they could be trained to return to their old haunts and establish new groups in Europe. To do this, the birds were given a human foster parent, who lived with them for nine months. Then, they were trained to fly after a microlite, and were eventually taught a migration route to Northern Italy.

Photo Two  By Richard Bartz, Munich aka Makro Freak - Own work, CC BY-SA 2.5,

Waldrapp Ibis (Geronticus eremita) (Photo Two)

What Portugal found was that these birds, who had human ‘parents’, automatically formed a V Formation when they flew, at 45 degrees to one another, approximately 1.2 metres apart. This was exactly as predicted by aerodynamic theory, which is based on fixed-wing planes. What the birds did was synchronise their wingbeats naturally to avoid generating turbulence between them. Each bird except the one right at the front rode on the updraft of the bird in front.

The group was dynamic, with no clear leader, though birds did seem to have a preference for their position, be it to the right or left, front or back.

However, the birds noticed how long another bird took at the front of the flock, and would then allow it to take a rest at the back, as if they had an innate sense of fairness.

What happened in the flock also depended on the ‘popularity’ of the individual bird. Portugal defined this as ‘the number of connections and interactions’ that a bird had with other birds. If an ‘unpopular’ bird stopped off for a rest, the others would look round, notice who it was, and then just keep going. If a ‘popular’ bird stopped, however, all the other birds would go down for a rest too. What we think of as ‘leadership’ might just be about a network of relationships instead.

Photo Three from

Waldrapp Ibis in flight (Photo Three)

Portugal finished his talk with something a bit closer to home: pigeons. Pigeons are about the maximum size for birds that fly in a cluster, and, unlike V Formation flying, being at the front of the group is good from an aerodynamic point of view, being at the back is bad.

Sadly, in pigeon society the popular/unpopular thing plays out in a different way. Shy pigeons are nearly always at the back. Bold, investigative pigeons are nearly always at the front. And unlike with geese and cranes, that’s the way it stays – if you’re a backmarker, that’s where you’ll stay.

Portugal had his pigeons fly over a number of routes. To start with, the group would be somewhat inefficient, but after a dozen flights they’d have the most direct route mapped, and that would be the one that they’d always follow. However, here’s the rub. After the flock had flown a route over a hundred times, he would take pigeons out for a solo flight. The ones who were always at the front came home pretty directly (though interestingly the flock as a whole always flew faster than a solo bird). But when he released a bird that had been at the back of the flock, they almost always either gave up and went to sit in a tree, or got lost, sometimes for days.

Were they just not paying attention? Or were they so intent on keeping up that they didn’t have the energy to see where they were going? Could they maybe not see the lead bird properly? All very good questions for which we have no answers. But how fascinating! I learned so much from this talk, and in particular I loved the clear structure, which makes it so much easier to take in and to remember – I’ve barely had to look at my notes while I’ve been writing this. Do pop over and have a look. I guarantee that you won’t be disappointed.

Photo Credits

Photo One By Myself (Adrian Pingstone). – My own photo, taken with a Nikon D5300 DSLR and Nikon 18-200 mm lens, Public Domain,

Photo Two By Richard Bartz, Munich aka Makro Freak – Own work, CC BY-SA 2.5,

Photo Three from

London Natural History Society Talks – An Introduction to Plant Galls by James Heal

Dear Readers, this talk exemplified why I am loving this series so much. James Heal is such an enthusiast that although I knew next to nothing about plant galls at the beginning, by the end I was desperate for spring to come so that I could go out gall-hunting. Heal endeared himself to me greatly by saying that he had a dream of giving up his job in finance so that he could become a gall-mite specialist. Who wouldn’t rather be a gall-mite specialist is my question, and I’m an accountant too. But let’s see first of all what a gall is.

We’ve all probably seen plant galls, even if we haven’t been aware of it.

Photo One by Lairich Rig / Silk button spangle galls on oak

Silk button spangle galls on oak (Photo One)

A gall is abnormal growth on a plant under the influence of another organism. So the ‘silk buttons’ above are actually created by the plant itself, due to chemicals produced by the invading organism. The gall involves the enlargement or proliferation (or both) of the cells or vascular tissue of the plant. This is produced for the nutrition and protection of the gall-inducing organism.

Photo Two by M J Richardson / Knopper gall on oak

Knopper gall on oak (Photo Two)

The great thing about galls (or one of the great things) is that they can be used to identify what caused them. Gall midges, for example (of which more later) are extremely difficult to identify to a species level from the insect, but the galls can be diagnostic.

So, how do you know what gall you’re looking at? Heal suggested a three-part approach:

Firstly, identify your plant. This might seem easy (‘It’s an oak’) but what kind of oak is it? There are some galls that we’ve all seen on lime leaves, even if we didn’t know what they were, but to identify the insect that caused them we need to know if we’re looking at a small-leaved lime, a broad-leaved lime or the very common hybrid between the two. Why is life never simple, I ask myself. Probably because it would be boring.

Having identified your species, it makes sense to take a good detailed note of where exactly on the plant you found the gall – leaf rib, body of the leaf, stem, bud?

Secondly, take a number of photos (if it’s a leaf, take both sides). If you can zoom in or magnify, that’s a good idea too. Many galls can be identified right down the species just through a good photo. If you want to become a serious galler (or Cecidologist) you might consider taking specimens and even rearing the inhabitants of the galls until they emerge, blinking, into the big wide world, but it’s not necessary for most people.

Thirdly, get yourself a good guide. If you are just beginning, Heal recommends this one:

But if you’re more serious, this is the one to go for, and apparently a new edition is due out soon.

And if you are really, really serious, the New Naturalist on plant galls has everything you ever wanted to know. This one is, I think, out of print, but you can get one-off reprints of New Naturalists if you go to their website, or second-hand bookshops will often have them. After all, plant galls are not the most apparently interesting of subjects, though after Heal’s talk I imagine there might be a run on the title.

Then, Heal moved on to talk about the different organisms that cause galls, and there are a fair few of them. After all, if you are a delicate little larva, how nice it must be to be surrounded by a robust protective covering while you munch away to your heart’s content, and many unrelated insect groups have taken this route.

First, we have the gall midges (Cedidomyiidae), members of the fly family (Diptera). These are tiny creatures, many of whom are less than a millimetre long. They have these remarkable antennae that look like strings of beads. Heal showed a number of photos of the midges causing the leaf to curl around: while we might see the caterpillars of species like the peacock butterfly making themselves a shelter by stitching the leaves of nettles together, with these midges the plant itself is persuaded to grow in an unnatural way. You can see a picture of ash mid-rib gall, caused by a gall midge, below.

Photo Three by By Alvesgaspar - Own work, CC BY-SA 3.0,

Gall midge (Photo Three)

Photo Four by By Alvesgaspar - Own work, CC BY-SA 3.0,

Ash Midrib gall (Photo Four)

Then there are the gall wasps (Cynipidae), who produce some of the most well-known and spectacular galls, such as the oak knopper gall in Photo Two, and the Robin’s pincushion on roses. Within that multicoloured mass of ‘hairs’ is a many-chambered gall, each containing a tiny wasp larvae. Heal points out that if you open up a gall caused by an insect, what pops out might not be the creature that made the gall but another species entirely that is either a parasite, a predator or some other kind of free-loader.

Photo Five by Trish Steel, CC BY-SA 2.0 <>, via Wikimedia Commons

Photo Five

Oyster gall on oak leaf

Then there are the gall mites (Eriophyidae), which are Heal’s favourite group, partly because they are so understudied and so it’s likely that there are some undiscovered species lurking in our back yards. They are not typically ‘mite-y’ looking, but, as Heal put it, they look more like carrots, long and slim. The gall that you might have seen most often is the Nail gall on lime leaves, which is rather beautiful in my opinion. Some of the galls contain microscopic ‘hairs’ which can be diagnostic for species. Some gall mites are pests of food crops, but others, such as the bindweed gall mite, are used for biological control of noxious weeds.

Photo Six By Rosser1954 Roger Griffith - Own work, Public Domain,

Lime Nail Gall (Photo Six)

Photo Seven By Unknown author - Australian Insect Common Names:, Public Domain,

A cereal rust mite (Photo Seven)

So, these are the three main groups of insects who can create galls, but there are many others; sawflies on willow, aphids on elm and some species of moth. Then there are the fungi that can induce galls. Mistletoe technically is a gall-causer – the tree produces distortion and swelling at the point of infection, induced by the parasite. And then there are endless bacteria and viruses that can cause galls.

Photo Nine by Lairich Rig / Leaf galls on crack willow

Galls on crack willow caused by a sawfly (Photo Eight)

So this was a most interesting talk by James Heal – he pitched it perfectly for beginners, I wouldn’t be the least bit surprised if a whole new bunch of gallers has been inspired by his presentation. I certainly learned a lot, and it’s left me with a whole lot of things to ponder. If you’d like to listen to the whole thing (which I would recommend) you can find the link here.

Photo Credits

Photo One by Lairich Rig / Silk button spangle galls on oak

Photo Two by M J Richardson / Knopper gall on oak

Photo Three by By Alvesgaspar – Own work, CC BY-SA 3.0,

Photo Four by © Copyright Lairich Rig and licensed for reuse under this Creative Commons Licence.

Photo Five by Trish Steel, CC BY-SA 2.0 <>, via Wikimedia Commons

Photo Six By Rosser1954 Roger Griffith – Own work, Public Domain,

Photo Seven By Unknown author – Australian Insect Common Names:, Public Domain,

Photo Nine by Lairich Rig / Leaf galls on crack willow

London Natural History Talks – Trees and Fungi by David Humphries

Dear Readers, this week’s talk was by David Humphries, Tree Management Officer for the City of London. He has been based in Hampstead Heath for 35 years, and recently won a special award for caring for London’s trees. I was really looking forward to this talk, and I wasn’t the only, as for the first time since the LNHS talks started, this one was sold out! Fortunately, you can still watch the whole thing here, and I’d recommend that you do so, as the photos were fantastic, and I can only capture the merest flavour of the range of the talk.

Humphries is something of a fungiphile: he gave us a quick look at his computer, where he has 22,000 photos of fungi, neatly arranged into 584 folders, one for each species. Most of them were taken on Hampstead Heath, which has over 25,000 trees, and where upwards of 600 fungal species have been recorded. Humphries thinks this is probably because, unlike in 1830 when John Constable painted a view of the Heath that shows it completely bereft of trees, there are now a substantial number of habitats and tree species.

First, we had a quick run through the variety of fungi that can be found in association with trees. There are the perennial bracket fungi such as hoof fungus (Fomes fomentarius) which persist for years. They form layers, as you can see from the photo below, but these are not necessarily annual – each layer is created when the fungus produces spores, and in one example that Humphries showed us later in the talk, it’s clear that they can be produced on multiple occasions in a single year if the conditions are right.

Incidentally, Otzi the iceman who was retrieved from a glacier in Austria and turned out to be about 5000 years old had some pieces of hoof fungus in his bag – it is used to produce amadou, which can be used as tinder. But as usual I digress.

Photo One by By George Chernilevsky - Own work, Public Domain,

Hoof fungus (Fomes fomentarius) (Photo One)

Then there are the annual bracket fungi, such as shaggy bracket (Inonotus hispidus) which produce fruiting bodies and spores and then die every year. They may remain in the same location for many years, and on the photos that Humphries shared you could see the scars of the previous generations on the bark.

Photo Two by Stu's Images, CC BY-SA 3.0 <>, via Wikimedia Commons

Shaggy bracket (Inonotus hispidus) (Photo Two)

However, with so many types of fungi, many looking superficially the same, how to ID them to species level? For some, you have to use microscopy of the spores, but Humphries had some general tips:

  • Take a slice through the fungus to look at the spore layer and the flesh
  • Have a look at the spore colour – anything from white to saffron to darkest inky black
  • Look in detail at the spore layer to see how the tubes from which the spores are released are coloured and shaped – Humphries recommended two useful resources:
  • If you are looking at a more typical ‘mushroom’, look at the gills and check to see whether they are attached to the stem or not (the word for where gills do form part of the stem is ‘decurrent’, a new word for me!)

Then, we moved on to the three ways in which fungi can be associated with trees.

  • Parasitic – it was Humphries view that parasitic fungi start to become problematic when a tree is weakened, either. A typical example would be honey fungus (Armillaria mellea)
Photo Three by Stu's Images, CC BY-SA 3.0 <>, via Wikimedia Commons

Honey Fungus (Armillaria mellea) (Photo Three)

  • Saprophytic – fungi that feed on fallen leaves, dead branches etc. They recycle nutrients that would otherwise not be released back into the soil. The earthstar that I found in St Pancras and Islington Cemetery would be an example.

  • And finally, there are the Mycorrhizal fungi. It’s only recently that we’ve learned what a vital part these fungi play in the health of plants – they form a mutualistic relationship with the roots of trees in this case, vastly extending the range of the roots in return for some of the benefits of photosynthesis. Some very familiar fungi, such as the edible boletus mushrooms and the traditional ‘toadstool’, Amanita muscari, are examples of mycorrhizal fungi. The fruiting bodies can often be seen exactly following the lines of the roots of the trees that are hosting them.
Photo Four by Amanita_muscaria_3_vliegenzwammen_op_rij.jpg: Onderwijsgekderivative work: Ak ccm, CC BY-SA 3.0 NL <>, via Wikimedia Commons

Amanita muscaria (Photo Four)

Humphries has, as you might expect, found some very interesting fungi in Hampstead, and one of the most attractive is the Many-Zoned Rosette (Podoscypha multizonata), of which the UK has about 80% of the European population. This is a rare species, which is being assessed by the IUCN for the Global Fungal Red List, and one reason for its rarity is that it is normally found on veteran oaks in oak pasture, a vanishingly rare habitat in the UK (though as I’m currently reading in Isabella Tree’s ‘Wilding’, it was probably once much more common. However, Humphries has noticed that the fungus has increased its range of hosts to include beech, hornbeam, lime, red and turkey oak and even horse chestnut, so maybe this bodes well for its future.

Photo Five by Lukas from London, England, CC BY-SA 2.0 <>, via Wikimedia Commons

Many-zoned Rosette (Podoscypha multizonata) (Photo Five)

As you might expect from someone who is involved in maintaining the health of trees, Humphries has a lot of interesting things to say about the different ways that fungi can infiltrate a tree. There are broadly three colonisation strategies.

The first is fungal-induced dysfunction, as favoured by our old friend honey fungus. Basically, rhizomorphs, which are a ‘rope’ of hyphae (the filaments of the fungi) travel through the soil and colonize a tree which already weakened. Once they’ve found such a tree, they fan out under the bark and infiltrate the vascular system, preventing the tree from transporting water and nutrients. In honey fungus the rhizomorphs are often called ‘bootlaces’ and you can see why.

Photo Six by Ericsteinert, CC BY-SA 3.0 <>, via Wikimedia Commons

Honey fungus rhizomorphs (Photo Six)

Secondly, some fungi infiltrate the sapwood when it’s suddenly exposed, whether by storm damage, lightning, injudicious pruning, or, in the case of the poor tree on my road, sudden collision with a skip. Examples include the beefsteak fungus, which at least has the benefit of being edible.

Photo Seven by Dan Molter, CC BY-SA 3.0 <>, via Wikimedia Commons

Beefsteak fungus (Fistulina hepatica) (Photo Seven)

And finally, there are the fungi that are living in the tree already, but which can only proliferate when the tree is weakened (endophytic fungi). These remind me a bit of the bacteria that live happily on our skin for ages, until our immune systems take a knock and then they lurch into action (Staphylococcus springs to mind). An insect attack, storm damage, root rock in high winds can all be starting points for such fungi (one example would be the birch polyphore (Fomitopsis betulinus). Humphries noted how, when a tree is cut down, these fungi can appear remarkably quickly once the sapwood is exposed to the air.

Photo Eight by Bernie Paquette, CC BY 4.0 <>, via Wikimedia Commons

Birch polyphore (Fomitopsis betulina) (Photo Eight)

Trees can live quite happily with fungal infestations, sometimes for decades. However, many fungi will eventually cause problems. Some cause white rot, which is where the wood turns white and spongy because the fungus has ‘eaten’ the lignin which provides stability – this is what honey fungus does. Some cause brown rot, which is where the cellulose is ‘eaten’ instead, and the tree becomes brittle – an example of this would be chicken of the woods (Laetiporus sulphureus). Some trees will eventually be hosts to both. And it isn’t just trees in forests, either.

Photo Nine by Gargoyle888., CC BY 3.0 <>, via Wikimedia Commons

Chicken of the woods (Laetiporus sulphureus) (Photo Nine)

Humphries mentioned two fungal diseases that are affecting that icon of the capital, the London Plane (Platanus x hispanica). One is Massaria Disease, caused by the fungus Splanchnonema platani. Humphries is of the opinion that this used to largely appear during droughts, but as most street trees have roots that are compacted, and as climate change affects rainfall in unpredictable ways, it has been seen in the UK. It normally causes branch fall in trees over 40 years old.

The second is elbowpatch crust (Fomitiporia punctata). According to the Forest Research UK site, this seems to affect a particular clone of the London Plane which has a propensity to develop weak forks. When infected by the fungus, it can drop whole branches, which is something of a health hazard considering how many there are.

Humphries spent some time explaining how part of his work is assessing trees, and deciding whether or not to save them, and how. There are various techniques that can be used to assess the amount of damage – a microdrill can be used to take a core through the tree without harming it, to see how far any rot has progressed. The whole tree can also be fitted with what sonic tomography receivers, which used sound waves to detect the integrity of the trunk – the photo of the tree in Humphries’s photo makes it look rather as if it’s getting an ECG. And there is much that often can be done, in terms of reducing the wind load that the plant has to bear in storms to prevent it being knocked over, and to support the tree. However, when the worst comes to the worst, the standing wood is endlessly useful for everything from beetles to woodpeckers, and fungi themselves are food for many invertebrates and other creatures (I’ve even watched a fox take a speculative bite out of a puffball.

However, the lockdowns and the increased footfall in Hampstead have caused additional challenges for fungi, and for the people who care about them. The big enemy seems to be compaction of the soil – no one seems to know how much this will damage the underground hyphae of the mycorrhizal fungi, without which many of the trees on the Heath will no longer thrive. Soil health is an issue for all of us, wherever we are, and it’s something to which we pay far too little attention in my view. I worry about the trampling in my local wood, but am also uncertain what we can do about it.

I really recommend this talk. It was stuffed full of information, and some of the photos that Humphries presented were wonderful. I learned so much, and I think I’ll probably watch it again to pick up some of the things that I missed or didn’t understand the first time round. So if you have an hour to spare and are wondering what to do during lockdown, here’s something to keep you entertained (along with all the other LNHS talks). The amazing world of fungi awaits!

Photo Credits

Photo One By George Chernilevsky – Own work, Public Domain,

Photo Two by Stu’s Images, CC BY-SA 3.0 <>, via Wikimedia Commons

Photo Three by Stu’s Images, CC BY-SA 3.0 <>, via Wikimedia Commons

Photo Four by Amanita_muscaria_3_vliegenzwammen_op_rij.jpg: Onderwijsgekderivative work: Ak ccm, CC BY-SA 3.0 NL <>, via Wikimedia Commons

Photo Five by Lukas from London, England, CC BY-SA 2.0 <>, via Wikimedia Commons

Photo Six by Ericsteinert, CC BY-SA 3.0 <>, via Wikimedia Commons

Photo Seven by Dan Molter, CC BY-SA 3.0 <>, via Wikimedia Commons

Photo Eight by Bernie Paquette, CC BY 4.0 <>, via Wikimedia Commons

Photo Nine by Gargoyle888., CC BY 3.0 <>, via Wikimedia Commons